Metal Roof Leaks: Screws, Seams and Flashing

Exposed-fastener metal roofs

Many homes, barns, shops and outbuildings here have screw-down metal panels. Each screw goes through the panel and seals with a rubber washer. That design is economical, but it means hundreds of holes in the roof, each depending on a washer that ages in sun and heat. See standing seam vs exposed fastener.

Common leak causes

• Washers that dry out and crack, letting water run down the screw.
• Loose or backed-out screws from panel expansion and contraction.
• Overdriven or angled screws that crushed or missed the washer.
• Screws that missed the purlin or framing below.
• Side and end laps without sealant or with failed sealant.
• Ridge caps, trim and wall flashing without closures or sealant.
• Rust at cut edges and scratches.

How metal roof leaks are repaired

Repairs start by finding which screws, laps or trim pieces are leaking. Worn fasteners are replaced, often with slightly larger screws with new washers so they bite into fresh metal. Failed lap sealant is cleaned and replaced, closures are added at ridges and eaves, and trim is reflashed. Widespread rust or many failed fasteners can point toward replacing panels or the roof. For shops and outbuildings, see metal and pole buildings.

Don't overtighten

More torque isn't better. A properly driven screw compresses the washer just enough to seal. Overdriving splits it.

For metal roof leaks on a home or outbuilding, call for roof repair.

Frequently Asked Questions

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